Technical Abstract:
Genetic improvement of crop plants has been traditionally achieved through conventional plant breeding. The art of plant breeding was developed long before the laws of genetics (the science of heredity) became known. The discovery of the principles of genetics at the turn of the last century boosted the growth of plant breeding, making it a science-based technology that has helped to bring about substantial improvement in crop plants. This process has often involved sexual hybridization with landraces and closely related species that possess certain desirable traits for incorporation into the crop species. Although generally slow and often tedious, traditional plant breeding, aided by knowledge from agronomy, cytogenetics, plant pathology, and entomology, continues to be the main means of crop improvement. Largely through exploitation of hybrid vigor, grain yields of several cereal crops were substantially increased (Duvick, 1992; Jauhar, 2003; Vasal et al., 2006). Interspecific hybridization, coupled with manipulation of chromosome pairing between the crop chromosomes and alien chromosomes, has helped in suitable modification of the genetic makeup of crop plants to the best advantage of humankind. Chromosomes are rod-like structures in the cells and carry desirable genes of interest. Sexual hybridization proved useful in moving, for example, genes for resistance to diseases and insect pests, from suitable alien donors into crop cultivars (Friebe et al., 1996; Fedak, 1999; Jauhar and Chibbar, 1999; Ceoloni and Jauhar, 2006; Jauhar, 2006a). However, failure to obtain sexual hybrids because of crossability barriers between species poses a significant limitation in conventional breeding. The advent of novel tools of direct gene transfers, which help asexually introduce new traits into plants that are otherwise very difficult to incorporate, are helping to speed up crop improvement (Vasil, 2003; Lapitan and Jauhar, 2006). Most major crops are being genetically transformed by directly shooting desirable genes into the tissues of otherwise desirable plants. The successful deployment of these biotechnological approaches to combat insect pests and diseases of important crops like rice, wheat, maize, barley and cotton is a remarkable accomplishment (Jauhar and Khush, 2002; Sahrawat et al., 2003; Walker-Simmons, 2003; Ramesh et al., 2004; Anand et al., 2004;). Nutritional enhancement of crops for alleviating malnutrition among the poor is another remarkable development in tackling global hunger and malnutrition. Thus, Golden Rice, which has been genetically endowed and instructed to produce both vitamin A and iron, has the real potential of saving millions of lives in impoverished countries (Ye et al., 2000; Beyer et al., 2002; Paine et al., 2005). Such a nutritional elevation of a cereal crop would be unthinkable by traditional breeding. The superior traits of golden rice can be easily transferred to other well-adapted rice cultivars through conventional breeding. Yet another exciting application of modern technology is in the production of edible vaccines for immunization against such deadly diseases as hepatitis B or tuberculosis, prevalent among the poor masses in Africa and Asia (Ariza, 2005; Kumar et al., 2005). Alvarez et al. (2006) have developed vaccines against pneumonia and bubonic plague orally immunogenic to mice. Certain crops, like the fruit crops or other horticultural crops may in the near future serve as vaccine factories and for acquiring immunity against a disease one may need to eat a banana or perhaps a tomato, instead of taking an injection. Other applications of this powerful technology are also outlined (Jauhar, 2006b). These newer approaches to crop improvement can effectively integrate with, but not replace, conventional breeding programs for maximum benefit to the human race, both rich and poor. The author strongly feels that modern biotechnology will help augment crop improvement and help sustain the global food supply (see Jauhar, 2006b). Modern biotechnology will constitute an important tool of future plant breeders.